Noble metal

About: Noble metal is a research topic. Over the lifetime, 15113 publications have been published within this topic receiving 337947 citations.

Recent developments in catalysis using nanostructured materials

Abstract: This review describes recent developments of size-, shape-, structure- and composition-dependent behavior of catalyst nanoparticles employed in alkylation, dehydrogenation, hydrogenation, and selective oxidation reactions for the conversion of hydrocarbons (with main emphasis on fossil resources) to chemicals. Innovation in these areas is largely driven by novel synthesis of (nano)porous and nanostructured catalytic materials. In case of alkylation, several new classes of porous materials have recently emerged as catalysts while the discovery of novel ultralarge-pore frameworks with desirable acidity remains largely a serendipitous process. Noble metal nanoparticles such as Pt, Pd, Rh, Au and their alloys with other metals have been extensively employed to catalyze a wide range of dehydrogenation, hydrogenation, and selective oxidation reactions of organic molecules. Novel approaches are still required to synthesize and characterize stable gold and other metal nanoparticles with tightly controlled sizes to further advance the knowledge of their unique size-dependent catalytic behavior. The bulk mixed metal oxides of vanadium, molybdenum, and other transition metals, such as the M1 phase for propane ammoxidation to acrylonitrile, have shown great promise as highly active and selective oxidation catalysts. However, fundamental understanding of surface molecular structure–reactivity relationships of these systems remains highly limited. Future advances in all these areas may be possible through combined experimental and theoretical approaches.

Hierarchical nanostructured NiCo2O4 as an efficient bifunctional non-precious metal catalyst for rechargeable zinc-air batteries.

Abstract: A nickel-doped cobalt oxide spinel structure is a promising non-precious metal electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal–air batteries and water electrolyzers operating with alkaline electrolytes. One dimensional NiCo2O4 (NCO) nanostructures were prepared by using a simple electrospinning technique with two different metal precursors (metal nitrate/PAN and metal acetylacetonate/PAN). The effect of precursor concentration on the morphologies was investigated. Single-phase, NCO with an average diameter of 100 nm, porous interconnected fibrous morphology was revealed by FESEM and FETEM analysis. The hierarchical nanostructured 1D-spinel NiCo2O4 materials showed a remarkable electrocatalytic activity towards oxygen reduction and evolution in an aqueous alkaline medium. The extraordinary bi-functional catalytic activity towards both ORR and OER was observed by the low over potential (0.84 V), which is better than that of noble metal catalysts [Pt/C (1.16 V), Ru/C (1.01 V) and Ir/C (0.92 V)], making them promising cathode materials for metal–air batteries. Furthermore, the rechargeable zinc–air battery with NCO-A1 as a bifunctional electrocatalyst displays high activity and stability during battery discharge, charge, and cycling processes.

Silver-catalysed reactions of alkynes: recent advances

Abstract: Silver is a less expensive noble metal. Superior alkynophilicity due to π-coordination with the carbon-carbon triple bond makes silver salts ideal catalysts for alkyne-based organic reactions. This review highlights the progress in alkyne chemistry via silver catalysis primarily over the past five years (ca. 2010-2014). The discussion is developed in terms of the bond type formed with the acetylenic carbon (i.e., C-C, C-N, C-O, C-Halo, C-P and C-B). Compared with other coinage metals such as Au and Cu, silver catalysis is frequently observed to be unique. This critical review clearly indicates that silver catalysis provides a significant impetus to the rapid evolution of alkyne-based organic reactions, such as alkynylation, hydrofunctionalization, cycloaddition, cycloisomerization, and cascade reactions.

Enhanced Catalytic Performance of Pt-Free Iron Phthalocyanine by Graphene Support for Efficient Oxygen Reduction Reaction

Abstract: It is commonly accepted that it is almost not possible to realize the large-scale practical application of fuel cells if the expensive noble metal-based electrocatalysts for oxygen reduction reactions (ORR) cannot be replaced by other low-cost, efficient, and stable ones. Herein, our studies demonstrate that iron phthalocyanine (FePc) supported on chemically reduced graphene through π–π interaction can act as a noble metal-free electrocatalyst with a comparable activity, long-term operation stability, and better tolerance to methanol crossover and CO poisoning compared with commercial Pt/C for ORR in alkaline media. The improved electrochemical activity and stability of FePc by graphene is mainly attributed to the inherent properties of graphene and the π-stacking interaction between FePc and planar aromatic structure of graphene. The as-prepared graphene–iron phthalocyanine (g-FePc) composite exhibits an efficient 4-electron pathway and can be used as a promising Pt-free ORR electrocatalyst.